Detector device of thread breakage on a sewing machine

ABSTRACT

A device for detecting the absence of thread in a sewing machine which will stop the machine after completion of the sewing cycle on the particular workpiece being sewn and which will prevent the start of the next sewing cycle until the thread is replaced for normal sewing machine operation.

United States Patent Marl'orio 1 June 24, 1975 154] DETECTOR DEVICE OF THREAD BREAKAGE ON A SEWING MACHINE 156] References Cited [75] Inventor: Nerino Marforio, Milan, Italy UNITED STATES PATENTS 2,483,138 9/1949 Helmer 112/219 A 173] Asslgnee' v'rgmm M'lam 3,168,881 2/1965 Morin 112/219 R Italy 3,413,794 12/1968 Bell et a1 ZOO/61.18 x 3,599,585 8/1971 Myrick 112/219 B X 122] 1974 3,687,095 8/1972 Jackson 200/6113 x 1211 Appl. No.1 461,842 3,783,811 1/1974 Schmedding et a1. ZOO/61.18 X

[30] Foreign Application Priority Data Pnmary Exammer jam6s Scott May 22, 1973 Italy 24370/73 [52] U S 0 200/61 18 200/61 13. 1 12/218 A device for detecting the absence of thread in a sewl lz/zlg ing machine which will stop the machine after comple- [5 I] In CI B65 25/ tion of the sewing cycle on the particular workpiece [58] Fie'ld 13 82 R being sewn and which will prevent the start of the next 200/82 C. 153 T; 19/2. .25, .26; 28/51, 53; 57/81; 66/163, 166; ll2/l21.ll, 121.12, 218 R-220; 139/353; 250/548; 226/11, 45

sewing cycle until the thread is replaced for normal sewing machine operation.

3 Claims, 4 Drawing Figures DETECTOR DEVICE OF THREAD BREAKAGE ON A SEWING MACHINE BACKGROUND OF THE INVENTION The present invention relates to a device for stopping a sewing machine whenever a thread breaks. More specifically, the device in question is preferably to be applied in the case of a sewing machine that is part of an automatic sewing component, but it may be applied to any type of sewing machine whatsoever.

In an automatic sewing unit, the starting of the machine is effected automatically, such as when the piece of material to be sewed covers up a photoelectric cell located in front of the machine, and the stopping of the machine also occurs automatically whenever the photoelectric cell is exposed to view.

The partially processed item is then automatically stacked or is sent on to other sewing or finishing units, often at the same working level as the first sewing machine. Known devices for stopping a machine when a thread breaks are designed to cause an instantaneous stopping of the sewing machine and, in the event that the machine is part of an automatic unit, this becomes a disadvantage, since this instantaneous stopping of the machine while the material is still beneath the working parts will prove a hindrance to the performance of any other work cycles in which the unit is involved. Furthermore, the operator will have to take action by removing the material from the machine, all of this entailing considerable loss of time. The purpose of the present invention is to allow the machine to operate, even when the thread is broken, until the material has cleared the working parts completely, more specifically until the machine is shut off automatically in the absence of any more material to work on, thereupon preventing the machine from starting any new sewing operation.

SUMMARY OF THE INVENTION The above purpose is achieved fully by the device according to the invention, which is characterized by the fact that it consists of devices that are sensitive to the presence or absence of a thread; interrupting devices, triggered by these sensors, which then break the circuit controlling the starting of the sewing machine whenever the thread is broken or absent; devices for excluding the above sensors during the sewing phase of the machine, these being controlled by the same devices that control the starting and stopping of the sewing machine.

The advantage of the device according to the invention, especially when an automatic sewing unit is involved, is that it considerably reduces the intervening action of the operator, since the material is automatically brought out of the operational zone of the machine, even when a thread is broken. Furthermore, there is no holdup in any of the operations that are to be performed by other components, subsequent to that of sewing. This and other characteristics will be more clearly defined by the following description of a preferred but not necessarily exclusive form of embodiment, given only by way of example and not as delimiting the invention, in connection with the drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a view in front elevation of the device according to the invention,

FIG. 2 is a plan view of the device in FIG. 1,

FIG. 3 is a side view of the device, and

FIG. 4 is a view in perspective of the device.

DESCRIPTION OF THE PREFERRED EMBODIMENT Numeral l in the FIGS. of drawing identifies generally an angular support bracket formed by a vertical wall 2 and a horizontal plane 3. To the vertical wall 2 is attached a thread guide 4 for directing a thread 5 from a supply spool (not shown) to a conventional disk tension device 6 that is attached to the vertical wall 2. Beneath the disk tension device 6, another thread guide 7 if provided which is also attached to the wall 2. The horizontal plane 3 is provided with a hole 8 (FIG. 4) through which the thread 5 passes, as well as two holes 9, into which screws (not shown) are inserted so as to attach the bracket 1 to a sewing machine of any type (not shown). On the undersurface of the horizontal plane 3 there is attached a microswitch 10 having a movable contact ll (FIG. I) that is activated by a thread detecting means such as a rod-shaped sensor 12, located above the plane 3. The rod-shaped sensor 12 is disposed so as to make contact with the thread 5 and is held by the thread in the position, as shown in FIG. 4 so that the movable contact II is held away from a stationary contact 13 (FIG. 1), which is connected to a plug 16 and is connected in series with a relay (not shown) that controls the starting of the sewing machine. The movable contact 11 is electrically connected to a positive pole 17 of the plug 16. In the event that the thread 5 is absent, the rod-shaped sensor 12 is displaced to a rest position, as indicated by the brokenline representation in FIG. 2. In this position, the movable contact 11 is displaced onto a stationary contact 15 of the microswitch 10, which is electrically connected to a warning light 14, located on the horizontal plane 3. The warning light 14 is also electrically connected to a negative pole 18 of the plug 16.

The plane 3 includes a projection 19, to which is attached a sensor displacing means or air cylinder 20 having a piston shaft 21, the free erd of which carries a circular plate 22 that is adapted to engage the rodshaped sensor 12 and move it from the position shown in FIG. 4 to that position shown in FIG. 2.

The supply of air to the cylinder 20 is controlled by the same device as the one that controls starting and stopping the sewing machine. This could be a photoelectric cell, or it could be any sort of manual control device.

The shaft 21 is extended from the cylinder 20 whenever the sewing machine is in operation, but is drawn into the cylinder whenever the machine is turned off.

The operation of the above stopping device will now be described.

In the rest position or in other words, when the sewing machine is standing idle, the piston shaft 2] is completely within its cylinder, as shown in FIG. 4, and not in contact with the rod sensor 12, which occupies the position shown in the abovementioned FIG. 4, provided the thread 5 is present. In this position the movable contact II is in engagement with the stationary contact 13, which is connected in series to the relay for controlling the starting of the sewing machine when properly activated.

Should the thread be absent, the rod sensor 12, which is biased by a switch means will move to the position indicated by numeral 12a in FIG. 2, and the movable contact 11 will pivot so as to engage the stationary contact 15, causing the warning light 14 to light up and the machine-starting relay to be deactivated. Thus when the thread Sis absent, a visual signal will be given by the warning light 14 and the sewing machine will not be able to operate.

The machine can only be started when the thread 5 is present which maintains the rod sensor in the position shown in FIG. 4 and the movable contact 11 connected to the stationary contact 13.

When the sewing machine is set in motion, such as by a signal from a photoelectric cell, a solenoid (not shown) is immediately activated and this feeds power to the air cylinder 20, whose shaft causes the circular plate 22 to act in opposition to the rod sensor 12, displacing it from its position of involvement with the thread, as shown in FIG, 4, to the solid line position shown in FIG. 2. This position of the rod sensor 12 still corresponds to the position of the movable contact ll being engaged with the stationary contact 13 of the microswitch l0, and the movable contact, now being in series with the relay that controls machine shutoff, keeps the relay activated and the machine operating.

If while the sewing machine is in operation the thread 5 should break, the machine will still continue to operate for the entire operational period, or for as long as the piston shaft 21 holds the rod sensor I2 in the position indicated in FIG. 2, which means that the movable contact 11 is engaged with the stationary contact 13.

At the end of a sewing operation, whenever the machine is shut off because no more material is being fed under the working parts and the piston shaft 21 is drawn into the cylinder 20, then the machine can no longer be started when the thread is absent, for the movable contact I] will be separated from the stationary contact 15.

In the form of embodiment described above, reference is made to a thread 5, which could be either a needle thread or a looper thread, and one could obviously provide as many sensors 12 as there are threads being used in the sewing machine with all of these sensors being movable by a single air cylinder or by several such cylinders.

It is further possible to replace the air cylinder with other suitable mechanical or electromagnetic devices.

What is claimed is:

I. In an electrically operated sewing machine having circuitry for operating the machine depending upon the presence or absence of fabric at the sewing station the combination of means to detect the presence of sewing thread at the sewing station and to cause stopping of the sewing machine only after no fabric is present at the sewing station and after no sewing thread is present, said means comprising, thread detecting means mounted for movement from an inoperative position to a plurality of operative positions, one of said positions being one in which contact between the detecting means and the thread occurs, when thread is present, switching means operated by said thread detecting means to close and to open the operating circuit of the sewing machine, and means for holding said thread detecting means in an operative position when fabric is present at the sewing station and for permitting said detecting means to move to an inoperative position if no thread is present and after all fabric is gone from the sewing station.

2. The electrically operated sewing machine according to claim I wherein said detecting means includes a rod-shaped sensor (12) having one end connected to said switching means and the opposite end disposed for engagement by said holding means.

3. The electrically operated sewing machine according to claim I wherein said holding means includes an air cylinder (20) having a piston shaft (21) movable to and from engagement with said detecting means. 

1. In an electrically operated sewing machine having circuitry for operating the machine depending upon the presence or absence of fabric at the sewing station the combination of means to detect the presence of sewing thread at the sewing station and to cause stopping of the sewing machine only after no fabric is present at the sewing station and after no sewing thread is present, said means comprising, thread detecting means mounted for movement from an inoperative position to a plurality of operative positions, one of said positions being one in which contact between the detecting means and the thread occurs, when thread is present, switching means operated by said thread detecting means to close and to open the operating circuit of the sewing machine, and means for holding said thread detecting means in an operative position when fabric is present at the sewing station and for permitting said detecting means to move to an inoperative position if no thread is present and after all fabric is gone from the sewing station.
 2. The electrically operated sewing machine according to claim 1 wherein said detecting means includes a rod-shaped sensor (12) having one end connected to said switching means and the opposite end disposed for engagement by said holding means.
 3. The electrically operated sewing machine according to claim 1 wherein said holding means includes an air cylinder (20) having a piston shaft (21) movable to and from engagement with said detecting means. 